Programmed Self-Assembly Systems of Amphiphilic Random Copolymers into Size-Controlled and Thermoresponsive Micelles in Water

Abstract

We report programmed self-assembly systems of amphiphilic random copolymers bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic alkyl pendants into size-controlled and thermoresponsive micelles in water. This system affords simultaneous and precise control of the size, aggregation numbers, and cloud point (Cp) of micelles in water by primary structure (pendant alkyl groups, composition, and chain length) that is programmed in the copolymers. Typically, random copolymers bearing PEG and alkyl pendants (butyl, octyl, dodecyl, and octadecyl groups) universally induce intermolecular self-assembly in water to produce uniform size micelles (<10 nm). The size is just determined by the content and alkyl pendant length of the hydrophobic monomers, independent of main chain length (below critical length for self-folding): The size increased with increasing the content and the pendant length. Design of hydrophobic alkyl groups with tuning composition allow us to widely control the size (molecular weight: 20K−1350K) and cloud point (from 45 to 85 °C) of the polymer micelles. We can thus tailor-make various micelles with identical size yet different Cp or those with identical Cp yet different size. Thanks to such dual controllability, selfsorting and stepwise thermoresponsive micelle systems were also created with blends of different copolymers; binary copolymers induced orthogonal self-assembly in water to provide discrete micelles with different size and cloud point.

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“…54,56,59,64 At the small-limit, the study of random copolymers has explored how random sequences may lead to the emergence of microphase separated structures or affect polymer miscibility. 51,[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] This is a traditional way of imbuing a polymer material with the advantageous properties of two monomer chemistries. 37 Theory often relates these local sequence effects to effective interaction parameters or other local physical parameters.…”

The effect of macromolecular structure on the rheology and surface properties of amphiphilic random polystyrene-r-poly(meth)acrylate copolymers prepared by RDRP

“…Amphiphilic copolymers have received great attention in recent years, due to their interesting rheological and surface properties, and for their ability to self-assemble in stable micelles or other aggregates in selected solvents. [1][2][3][4][5] The self-assembly in micelles is known to happen above a certain critical micellar concentration (CMC), which is an important parameter to consider when comparing different amphiphilic copolymers and their solution properties. Indeed, it is known that the CMC is affected by many factors, such as the molecular weight and polydispersity, the chemical structure of the polymers, and the balance between the hydrophilic and hydrophobic moieties in the polymer.…”